Intertidal seagrass & sand – what do we value? Healthy intertidal flats are more than just beautiful places to cast a line or go for a stroll. They are productive areas, providing benefits to people, industry and the environment.
Who lives there?
Seagrasses
Migratory shorebirds
Fish
Resident shorebirds
Minute bottomdwelling plants
Pippies
Flounder
Heart urchin
Snails
Rays
Black swans
Sand worms
Crabs
Garfish
People
Terns and gulls
High tide Mid tide Low tide
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What are the benefits of healthy intertidal flats? 1. Seagrass stabilises the vast areas of intertidal sand and helps prevent erosion Seagrass roots anchor sand and reduce its tendency to move around with water movement. Areas stabilised by seagrass provide safe living places for other wildlife such as snails and urchins that are part of the food chain of the intertidal flats.
As the tide rises, beds of seagrass in the intertidal zone reduce the energy of wind waves and help prevent erosion. Predictable water movements and stable sea beds support aquaculture. They also help prevent erosion, benefiting coastal landholders.
2. Seagrass and small bottom dwelling plants are the basis of intertidal foodwebs Some animals (e.g. snails) feed directly on seagrass. Seagrass also provides a base for other plants (epiphytes) that contribute to intertidal primary production.
Seagrass breaks down to form detritus. This is easier to digest and supports many more animals than direct grazing on seagrass.
Resident and migratory shorebirds forage on wildlife supported by seagrass food webs.
Intertidal foodwebs support human food species along with the plants and animals that these species rely on for their food.
3. Seagrass and sandflats helps to keep the water clean and clear Seagrass and sandflats remove nutrients from the water and process them in various ways, helping to prevent algal blooms and keeping water clean and clear.
Clear water lets the full spectrum of sunlight to reach the seabed, allowing the growth of bottom-dwelling species that contribute to intertidal foodwebs.
Seagrass traps and filters sediment and absorbs nutrients from land-based activities, helping keep water clean and clear.
Clean clear water supports aquaculture and fisheries.
4. The intertidal flats of Robbins Passage and Boullanger Bay sequester and store carbon The vast seagrass beds of the intertidal zone continually take in carbon dioxide from the air and the sea and store it by converting it to living plant matter.
Within the sands of far NW Tasmania are peaty deposits that may be remnants of swamps from 20-40,000 years ago. These peaty deposits are storing fossil carbon.
5. The intertidal flats provide social and cultural benefits The intertidal flats of Robbins Passage and Boullanger Bay give both locals and tourists a place for recreation, educational opportunities and communing with nature. Thus, these sandy expanses contribute to the region’s growing ecotourism industry while supporting local culture and ways of life. Created by Blue Wren Group, University of Tasmania for the Cradle Coast Authority. Illustration by Jan Tilden, 2010.
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